JP4911168B2 - Wireless communication system, base station, wireless communication method, program - Google Patents

Description

  The present invention relates to a wireless communication system, a base station, a wireless communication method, and a program.

  In the WiMAX (Worldwide Interoperability for Microwave Access) Forum, the WiMAX System Profile is formulated based on the IEEE (Institute of Electrical and Electronic Engineers) 802.16e standard. A WiMAX wireless communication system is disclosed in Patent Document 1, for example.

  In a WiMAX wireless communication system, data is transmitted and received in sub-frame units, an OFDMA (Orthogonal Frequency Division Multiple Access) method is adopted as a multiple access method, and a TDD (Time Division) is used as a duplex method. Duplex) method is adopted.

  The OFDMA system is a sub-channel in the frequency direction and a symbol in the time direction, and a band is provided to a mobile station (MS), which is a slot unit representing the divided area. Is a method of assigning.

  The TDD scheme uses the same frequency for a DL (Down Link) link and a UL (Up Link) link between a base station BS (Base Station) and an MS, and uses a DL subframe and a UL sub on the time axis. This is a method of switching frames.

  Here, an outline of a frame structure in the WiMAX wireless communication system will be described with reference to FIG.

  Referring to FIG. 5, the WiMAX frame structure is a structure in which a DL subframe and a UL subframe are switched on a time axis (TDD method). A gap time called TTG (Transmit / Receive Transition Gap) and RTG (Receive / Transmit Transition Gap) exists between the DL subframe and the UL subframe.

  In the DL subframe and the UL subframe, a band is allocated to the MS in slot units, and data is transmitted using the allocated band (OFDMA scheme).

  In the DL subframe, a preamble area including a pilot signal is arranged at the head, and subsequently, a MAP area including a signal indicating which slot is allocated to each MS in the DL subframe and the UL subframe. Subsequent areas (DL Burst) are allocated to each MS as a band for transmitting DL data.

  On the other hand, in the UL subframe, a ranging area including a ranging signal for executing ranging for adjusting timing, frequency, and power on the MS side is arranged at the head. Subsequent areas (UL Burst) are allocated to each MS as a band for transmitting UL data.

  The WiMAX wireless communication system supports an adaptive modulation system. The adaptive modulation scheme is a scheme that adaptively changes the modulation scheme and coding rate of DL data and UL data between the BS and the MS in accordance with the MS propagation environment. In WiMAX, a data transmission rate is defined according to a combination of a modulation method and a coding rate, and this data transmission rate is called a physical rate.

  The WiMAX wireless communication system also supports a QoS (Quality of Service) class. That is, in the WiMAX wireless communication system, specific QoS classes such as UGS (Unsolicited Grant Service), ERT-VR (Extended Real Time-Variable Rate Service), RT (Real Time) -VR, NRT (Non Real Time) -VR. Bandwidth guarantee is performed for MSs belonging to.

  Here, in the WiMAX wireless communication system, an adaptive modulation operation for an MS belonging to a QoS class requiring bandwidth guarantee will be described with reference to FIG.

  In FIG. 6, the lower diagram shows the positional relationship between the BS and the MSs # 1 to MS # 3 belonging to the QoS class that requires bandwidth guarantee, and the upper diagram shows the positional relationship shown in the lower diagram. , DL subframes transmitted from the BS to the MS # 1 to MS # 3 are shown (hereinafter the same in FIG. 3 and FIG. 7).

  Referring to FIG. 6, it is assumed that MS # 1 to MS # 3 are located near the BS, that is, near the center of the cell in the initial state (state 1).

  The MS can transmit data at a high physical rate when it is near the center of the cell. Therefore, in state 1, the BS uses, for example, a high physical rate 16QAM (Quadrature Amplitude Modulation) 3/4 (the first half is the modulation scheme) as a combination of the modulation schemes and coding rates of MS # 1 to MS # 3. The latter half indicates the coding rate, and the same applies hereinafter. Hereinafter, an area to which 16QAM 3/4 is applied is referred to as a 16QAM area.

  In addition, the number of slots required for bandwidth guarantee varies depending on the physical rate, and a larger number of slots is required at a low physical rate. In state 1, since 16QAM 3/4 applied to MS # 1 to MS # 3 has a high physical rate, the number of slots required for guaranteeing the bandwidth of MS # 1 to MS # 3 is small. Therefore, the BS can accommodate all MS # 1 to MS # 3, and the bandwidth of the DL subframe is increased.

  Subsequently, it is assumed that MS # 1 leaves the 16QAM area and moves in the cell edge direction (state 2).

  Then, the BS applies, for example, QPSK (Quadrature Phase Shift Keying) 1/2 of a low physical rate as a combination of the modulation scheme and coding rate of MS # 1 by adaptive modulation. Hereinafter, an area to which QPSK 1/2 is applied is referred to as a QPSK area. Also, since QPSK 1/2 applied to MS # 1 is a low physical rate, the number of slots required for MS # 1 bandwidth guarantee increases.

  However, in state 1, since there is a lot of bandwidth in the DL subframe, even if the number of slots required for the bandwidth guarantee of MS # 1 increases in state 2, the BS does not change MS # 1 to MS # 3. All can be accommodated. However, since MS # 1 occupies the bandwidth, the DL subframe bandwidth is reduced.

  Subsequently, it is assumed that MS # 2 moves from the 16QAM area to the QPSK area (state 3).

  Then, the BS applies QPSK 1/2 of a low physical rate as a combination of the modulation scheme of MS # 2 and the coding rate by adaptive modulation.

  However, in state 2, since there is little free bandwidth in the DL subframe, in state 3, the BS cannot allocate a band corresponding to the physical rate of QPSK 1/2 to MS # 2, and MS # 2 The physical rate will decrease. Further, since there is no slot to be assigned to MS # 3, it is not possible to assign a slot until the next subframe.

  Therefore, in the WiMAX wireless communication system, control called Admission Control can be performed in the BS in order to avoid the above-described problem. Admission Control here refers to admission control for adaptive modulation. In the BS, MSs belonging to a QoS class requiring bandwidth guarantee among MSs performing adaptive modulation are controlled, and the MSs to be controlled are controlled. Is a control for determining whether or not the mobile station can be accommodated when adaptive modulation is performed. As a result of the determination, the BS does not change the physical rate for the MS determined to be unacceptable.

  Here, in the WiMAX wireless communication system, an adaptive modulation operation accompanied by an Admission Control for an MS belonging to a QoS class requiring bandwidth guarantee will be described with reference to FIG. In FIG. 7, the positional relationship in the lower diagram is the same as that in FIG. 6.

  Referring to FIG. 7, it is assumed that MS # 1 to MS # 3 are located in the 16QAM area in the initial state (state 1), as in FIG. At this time, a band is allocated to MS # 1 to MS # 3, as in FIG. 6, and the bandwidth is increased.

  Subsequently, it is assumed that MS # 1 moves from the 16QAM area to the QPSK area (state 2).

  Then, the BS executes the Admission Control for MS # 1, and when performing adaptive modulation with QPSK 1/2 for MS # 1 in Admission Control, the BS responds to the physical rate of QPSK 1/2. It is determined whether or not the bandwidth can be assigned to MS # 1. At this time, in state 1, since there is a lot of bandwidth in the DL subframe, the BS determines that bandwidth can be allocated for MS # 1 and can be accommodated in its own station. Therefore, the BS accommodates all the MS # 1 to MS # 3 even in the state 2. However, since MS # 1 occupies the bandwidth, the DL subframe bandwidth is reduced.

  Subsequently, it is assumed that MS # 2 moves from the 16QAM area to the QPSK area (state 3).

Then, the BS executes an Admission Control for MS # 2 as in the case of MS # 1. However, in state 2, since the bandwidth of the DL subframe is small, the BS determines that it is impossible to allocate the bandwidth to MS # 2. As a result, MS # 2, which cannot use an appropriate physical rate, frequently encounters communication errors and falls off the BS entry. In this case, MS # 2 is unfair because it has the same priority as MS # 1.
JP 2007-266719 A

  As described above, in the WiMAX wireless communication system, when the Admission Control is executed, the BS is premised on that all MSs are uniformly operated with the lowest physical rate QPSK 1/2.

  Therefore, when a certain MS is located at the edge of a cell, it is possible to guarantee a band according to QPSK 1/2 having the lowest physical rate, but on the other hand, a physical rate larger than QPSK 1/2 is assumed. There is a problem that the service is unacceptable.

  In addition, since it is assumed that the physical rate is the lowest QPSK 1/2, when the MS that requires a high physical rate is accommodated, even when the Admission Control is executed, the remaining MS is compressed in bandwidth. However, there is a problem that unfairness such as being unable to perform adaptive modulation and being out of entry may occur.

  Therefore, an object of the present invention is to provide a wireless communication system, a base station, a wireless communication method, and a program that solve the above-described problems.

The wireless communication system of the present invention includes:
The adaptive modulation is performed on a terminal to be controlled and belonging to a QoS (Quality of Service) class that requires bandwidth guarantee among terminals that perform adaptive modulation that adaptively changes a combination of a modulation scheme and a coding rate. A base station that executes control to determine whether or not it can be accommodated in the own station when executed,
The base station
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination unit that determines a minimum physical rate for performing bandwidth guarantee based on the comparison result;
A control unit that executes the control on the premise that adaptive modulation is performed at the lowest physical rate determined by the determination unit for the terminal to be controlled.

The base station of the present invention
Among the terminals that perform adaptive modulation that adaptively changes the combination of modulation scheme and coding rate, the terminal to be controlled that belongs to the QoS class that requires band guarantee is accommodated in its own station when the adaptive modulation is performed. A base station that executes control for determining whether or not it is possible,
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination unit that determines a minimum physical rate for performing bandwidth guarantee based on the comparison result;
A control unit that executes the control on the premise that adaptive modulation is performed at the lowest physical rate determined by the determination unit for the terminal to be controlled.

The wireless communication method of the present invention includes:
Among the terminals that perform adaptive modulation that adaptively changes the combination of modulation scheme and coding rate, the terminal to be controlled that belongs to the QoS class that requires band guarantee is accommodated in its own station when the adaptive modulation is performed. A wireless communication method by a base station that executes control to determine whether or not possible,
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination step for determining a minimum physical rate for performing bandwidth guarantee based on the comparison result;
A control step of executing the control on the premise that adaptive modulation is executed at the determined minimum physical rate for the terminal to be controlled.

The program of the present invention
Among the terminals that perform adaptive modulation that adaptively changes the combination of modulation scheme and coding rate, the terminal to be controlled that belongs to the QoS class that requires band guarantee is accommodated in its own station when the adaptive modulation is performed. To the base station that executes control to determine whether or not it is possible,
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination procedure for determining a minimum physical rate for performing bandwidth guarantee based on the comparison result;
A control procedure for executing the control on the premise that adaptive modulation is executed at the determined minimum physical rate for the terminal to be controlled.

  In the present invention, the minimum guaranteed rate of the control target terminal in the control for determining whether or not the control target terminal belonging to the QoS class requiring bandwidth guarantee can be accommodated in the own station when adaptive modulation is performed. It is assumed that the system is operated at the minimum physical rate according to the system.

  Therefore, the control target terminal is guaranteed a band according to the minimum physical rate based on the minimum guaranteed rate, and an effect that the service based on the minimum physical rate can be permitted is obtained.

  Also, since it is premised on the operation at the minimum physical rate according to the minimum guaranteed rate of the terminal to be controlled, control is performed even when a terminal requiring a high physical rate is accommodated or when the above control is executed. An effect is obtained that it is possible to avoid that the target terminal occupies the band.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the following embodiments, a case where the wireless communication system is a WiMAX wireless communication system will be described as an example, but the present invention is not limited to this.

  As shown in FIG. 1, the wireless communication system according to the present embodiment includes a BS that is a base station and MSs # 1 to # 3 that are terminals. In FIG. 1, the number of BSs and MSs is one and three for simplification of explanation, but the present invention is not limited to this. Further, it is assumed that the MSs # 1 to # 3 are terminals belonging to a QoS class that requires bandwidth guarantee.

  The BS includes a radio communication unit 11 and a base station operation unit 12.

  The wireless communication unit 11 performs wireless communication with the MSs # 1 to # 3.

  The base station operation unit 12 includes a minimum physical rate determination unit 13 and an admission control unit 14 serving as a control unit.

  The lowest physical rate determination unit 13 determines the lowest physical rate that is the lowest physical rate for performing bandwidth guarantee for each of the MSs # 1 to # 3. A method for determining the minimum physical rate will be described later.

  The Admission Control unit 14 performs adaptive modulation at the lowest physical rate determined by the lowest physical rate determination unit 13 for the control target MS belonging to the QoS that requires bandwidth guarantee among the MSs that perform adaptive modulation. If it is assumed, the Admission Control is executed to determine whether or not the mobile station can be accommodated.

  Specifically, the Admission Control unit 14 determines that the MS can be accommodated in the own station if it can allocate a band corresponding to the minimum physical rate determined by the minimum physical rate determination unit 13 for the control target MS.

  In addition, although not shown, the base station operation unit 12 has means equivalent to a BS generally used in a WiMAX wireless communication system. For example, there are means for executing network entry processing with MS # 1- # 3, means for generating a service flow with MS # 1- # 3, and the like. However, such means are not an essential part of the present invention, and since well-known means can be used, detailed description thereof is omitted.

  The MS # 1 includes a wireless communication unit 21 and a terminal operation unit 22. Although not shown, MS # 2 and # 3 also have the same means as MS # 1.

  The wireless communication unit 21 performs wireless communication with the BS.

  Although not shown, the terminal operation unit 22 has means equivalent to an MS generally used in a WiMAX wireless communication system. For example, there are means for executing network entry processing with the BS, means for generating a service flow with the BS, and the like. However, such means are not an essential part of the present invention, and since well-known means can be used, detailed description thereof is omitted.

  Hereinafter, the operation of the wireless communication system of the present embodiment will be described.

[Operation until service flow is generated]
First, an operation until a service flow is generated between the BS and the MSs # 1 to # 3 will be described with reference to FIG. Here, a case where a service flow is generated between the BS and the MS # 1 is taken as an example.

  First, the BS performs network entry processing for allowing MS # 1 to enter an ASN (Access Service Network) and CSN (Connectivity Service Network) (not shown) with MS # 1 (step S201).

  When the network entry process is completed, the process proceeds to a service flow generation process.

  In the service flow generation process, first, the BS gives information on additional information (for example, the minimum guaranteed traffic rate of MS # 1) necessary for providing service to MS # 1 to MS # 1. Etc.), a DSA (Dynamic Service Addition) -REQ (Request) message is transmitted (step S202).

  In response, MS # 1 transmits a DSA-RSP (Response) message to the BS as a response to the DSA-REQ message (step S203). When MS # 1 wants to change the additional information designated by the BS, the additional information to be changed is included in the DSA-RSP message and sent back to the BS. When the additional information is not changed, the DSA-RSP Only the message body is returned to the BS.

  Thereafter, the BS transmits a DSA-ACK (Acknowledgement) message indicating that reception of the DSA-RSP message is completed to MS # 1 (step S204).

  Thus, the service flow generation process is completed.

[Adaptive modulation operation with Admission Control]
Next, an adaptive modulation operation with Admission Control will be described with reference to FIG. In FIG. 3, the positional relationship in the lower diagram is the same as that in FIGS.

  Referring to FIG. 3, it is assumed that MS # 1 to MS # 3 are located in the 16QAM area in the initial state (state 1).

  At this time, the BS has already completed the above-described service flow generation process with each MS # 1 to MS # 3.

  Therefore, the minimum physical rate determination unit 13 of the BS allows permissible throughput that represents the throughput that can be secured in each MS when the number of MSs accommodated in the BS is accommodated in advance for each combination of modulation scheme and coding rate. For each MS # 1 to # 3, when the service flow generation process is completed, the allowable throughput and the minimum guaranteed rate are compared, and the minimum physical rate is determined based on the comparison result.

  Here, a method of determining the minimum physical rate will be described in detail with reference to FIG.

  Here, the minimum physical rate is determined under the following conditions.

(conditions)
-Frequency band used in wireless communication system = 10 MHz
・ Assumed number of MSs = 4 ・ DL: UL ratio, which is a symbol ratio of DL subframe and UL subframe = 29: 18
・ Minimum guaranteed DL rate provided to controlled MS = 1 Mbps
-Minimum guaranteed rate of UL provided to controlled MS = 500 kbps
First, the minimum physical rate determination unit 13 obtains the number of usable slots in the DL subframe and the UL subframe.

  Here, it is assumed that 390 slots for 13 symbols × 30 subchannels in the DL subframe and 175 slots for 5 symbols × 35 subchannels in the UL subframe can be used for band allocation to the MS.

  Next, the minimum physical rate determination unit 13 obtains the upper limit number of slots per MS when 4 assumed MSs are accommodated in the BS.

  Here, in the case of a DL subframe, since the number of usable slots is 390, the upper limit is 97 slots. In the case of a UL subframe, since the number of usable slots is 175, the upper limit is 43 slots.

  Next, the minimum physical rate determination unit 13 calculates an allowable throughput when 4 assumed MSs are accommodated in the BS for each combination of modulation scheme and coding rate.

  Here, the number of bytes that can be assigned to one slot in each combination = A, the number of frames transmitted per second between the BS and the MS = 200, and the upper limit number of slots per MS determined above is used, The allowable throughput is calculated for each of DL and UL according to the following formula (1). Here, “8” is a coefficient for converting bytes into bits.

(Maximum number of slots per MS) x A x 200 x 8 (1)
Thereafter, the minimum physical rate determination unit 13 compares the allowable throughput of each combination with the minimum guaranteed rate for each of DL and UL, and determines the minimum physical rate based on the comparison result.

  Here, in the case of DL, the minimum guaranteed rate is 1 Mbps. The minimum allowable throughput that satisfies this minimum guaranteed rate is the allowable throughput of QPSK 3/4. Therefore, the minimum physical rate of DL is determined to be a physical rate of QPSK 3/4. Similarly, in the case of UL, the minimum guaranteed rate is 500 kbps, and the minimum allowable throughput that satisfies this minimum guaranteed rate is the allowable throughput of QPSK 3/4. Therefore, the minimum physical rate of UL is also determined to be the physical rate of QPSK 3/4.

  Note that the minimum physical rate determining unit 13 may monitor the number of MSs actually accommodated in the BS and determine the assumed accommodated number based on the monitoring result. For example, it is conceivable to monitor the number of MSs regularly and determine the average number of units in a certain period as the assumed number of units.

  Therefore, for each of MS # 1 to MS # 3, the bandwidth required when the Admission Control is generated can be estimated in advance by using the minimum physical rate determined by the minimum physical rate determination unit 13. FIG. become that way.

  Referring to FIG. 3 again, it is assumed that MS # 1 has moved from the 16QAM area to the QPSK area (state 2).

  Then, the Admission Control unit 14 of the BS executes Admission Control on the premise that adaptive modulation is performed at the lowest physical rate determined by the lowest physical rate determining unit 13 for MS # 1.

  The minimum physical rate assumed at this time is not uniformly the physical rate of QPSK 1/2, but the minimum physical rate corresponding to the minimum guaranteed rate of MS # 1. Therefore, MS # 1 is guaranteed a band according to the minimum physical rate, and can accept a service based on the minimum physical rate.

  Further, if the minimum physical rate is higher than the physical rate of QPSK 1/2, the number of slots required for the bandwidth guarantee of MS # 1 does not become larger than the number of slots in the case of QPSK 1/2. Therefore, even if adaptive modulation is performed on MS # 1, MS # 1 can be accommodated, and it is avoided that MS # 1 occupies a band.

  Subsequently, it is assumed that MS # 2 moves from the 16QAM area to the QPSK area (state 3).

  Then, the Admission Control unit 14 of the BS executes Admission Control on the premise that adaptive modulation is performed at the lowest physical rate determined by the lowest physical rate determining unit 13 for MS # 2.

  As in the case of MS # 1, the minimum physical rate assumed at this time is not uniformly the physical rate of QPSK 1/2, but the minimum physical rate corresponding to the minimum guaranteed rate of MS # 2. Become. Therefore, MS # 2 is guaranteed a band according to the minimum physical rate, and can accept a service based on the minimum physical rate.

  If the minimum physical rate is higher than the physical rate of QPSK 1/2, the number of slots required for the bandwidth guarantee of MS # 2 is the slot for QPSK 1/2 as in the case of MS # 1. Not much compared to the number. In state 2, MS # 1 does not occupy the band. Therefore, even if adaptive modulation is performed on MS # 2, MS # 2 can be accommodated, and unfairness does not occur between MS # 1 and MS # 2. Further, since it is avoided that MS # 1 and MS # 2 occupy a band, it is possible to allocate a band to MS # 3.

  As described above, in the present embodiment, for each combination of modulation scheme and coding rate, the BS calculates the allowable throughput of each MS when the BS accommodates the assumed number of MSs, and controls the Admission Control. For the target MS, the minimum physical rate is determined based on the comparison result between the minimum guaranteed rate of the MS and the allowable throughput, and Admission Control is executed on the assumption that adaptive modulation is performed at the determined minimum physical rate.

  As described above, the minimum physical rate assumed in the Admission Control is not uniformly the physical rate of QPSK 1/2, but is the minimum physical rate corresponding to the minimum guaranteed rate of the MS to be controlled. Therefore, the control target MS is guaranteed a band according to the minimum physical rate, and can allow a service based on the minimum physical rate.

  If the minimum physical rate is higher than the physical rate of QPSK 1/2, the number of slots required for guaranteeing the bandwidth of the MS to be controlled is not much larger than the number of slots in the case of QPSK 1/2. . Therefore, even if adaptive modulation is performed on the control target MS, the control target MS can be prevented from occupying a band.

  Further, since it is possible to avoid the occupation of the band by the MS to be controlled, even when an MS that requires a high physical rate is accommodated, even when the Admission Control is executed, the band is compressed and adaptive modulation is not performed. It is possible to reduce the possibility that unfairness such as failure to enter and entry will occur. Further, since an extra bandwidth is generated, the extra bandwidth can be assigned to an MS belonging to a QoS class such as BE (Best Effort Service) that does not require bandwidth guarantee.

  The method performed in the BS of the present invention may be applied to a program for causing a computer to execute. In addition, the program can be stored in a storage medium and can be provided to the outside via a network.

It is a block diagram which shows the structure of the radio | wireless communications system of one Embodiment of this invention. 2 is a flowchart for explaining an example of operations from network entry processing to service flow generation processing in the wireless communication system shown in FIG. 1. It is a figure explaining an example of the adaptive modulation operation | movement in the radio | wireless communications system shown in FIG. It is a figure explaining an example of the determination method of the minimum physical rate in the minimum physical rate determination part shown in FIG. It is a figure explaining the frame structure of WiMAX. It is a figure explaining an example of the adaptive modulation operation | movement in the related radio | wireless communications system. It is a figure explaining the other example of the adaptive modulation operation | movement in the related radio | wireless communications system.

Explanation of symbols

BS base station MS # 1 to MS # 3 terminal 11 radio communication unit 12 base station operation unit 13 minimum physical rate determination unit 14 admission control unit 21 radio communication unit 22 terminal operation unit

Claims (16)

The adaptive modulation is performed on a terminal to be controlled and belonging to a QoS (Quality of Service) class that requires bandwidth guarantee among terminals that perform adaptive modulation that adaptively changes a combination of a modulation scheme and a coding rate. A base station that executes control to determine whether or not it can be accommodated in the own station when executed,
The base station
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination unit that determines a minimum physical rate for performing bandwidth guarantee based on the comparison result;
And a control unit that performs the control on the premise that adaptive modulation is performed at the lowest physical rate determined by the determination unit for the terminal to be controlled.   2. The radio according to claim 1, wherein the determination unit specifies a combination having the lowest allowable throughput that satisfies the minimum guaranteed rate among the combinations, and determines a physical rate of the specified combination as the lowest physical rate. Communications system.   3. The control unit according to claim 1, wherein the control unit determines that the terminal can be accommodated if the bandwidth corresponding to the lowest physical rate determined by the determination unit can be allocated to the terminal to be controlled. Wireless communication system.   The wireless unit according to any one of claims 1 to 3, wherein the determination unit monitors the number of terminals actually accommodated in the own station and determines the predetermined accommodation number based on the monitoring result. Communications system. Among the terminals that perform adaptive modulation that adaptively changes the combination of modulation scheme and coding rate, the terminal to be controlled that belongs to the QoS class that requires band guarantee is accommodated in its own station when the adaptive modulation is performed. A base station that executes control for determining whether or not it is possible,
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination unit that determines a minimum physical rate for performing bandwidth guarantee based on the comparison result;
And a control unit that executes the control on the premise that adaptive modulation is performed at the lowest physical rate determined by the determination unit for the terminal to be controlled.   The base according to claim 5, wherein the determination unit specifies a combination having the lowest allowable throughput that satisfies the minimum guaranteed rate among the combinations, and determines a physical rate of the specified combination as the minimum physical rate. Bureau.   7. The control unit according to claim 5, wherein the control unit determines that the terminal can be accommodated if the bandwidth corresponding to the lowest physical rate determined by the determination unit can be allocated to the terminal to be controlled. 8. Base station.   The base according to any one of claims 5 to 7, wherein the determination unit monitors the number of terminals actually accommodated in the own station and determines the predetermined accommodation number based on the monitoring result. Bureau. Among the terminals that perform adaptive modulation that adaptively changes the combination of modulation scheme and coding rate, the terminal to be controlled that belongs to the QoS class that requires band guarantee is accommodated in its own station when the adaptive modulation is performed. A wireless communication method by a base station that executes control to determine whether or not possible,
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination step for determining a minimum physical rate for performing bandwidth guarantee based on the comparison result;
A control step of performing the control on the premise that adaptive modulation is performed at the determined minimum physical rate for the terminal to be controlled.   10. The radio according to claim 9, wherein, in the determining step, a combination having the lowest allowable throughput that satisfies the minimum guaranteed rate is specified from the combinations, and a physical rate of the specified combination is determined as the lowest physical rate. Communication method.   The wireless communication according to claim 9 or 10, wherein, in the control step, if it is possible to allocate a band corresponding to the determined minimum physical rate for the terminal to be controlled, it is determined that the terminal can be accommodated in the own station. Method.   The radio according to any one of claims 9 to 11, wherein in the determining step, the number of terminals actually accommodated in the own station is monitored, and the predetermined accommodated number is determined based on the monitoring result. Communication method. Among the terminals that perform adaptive modulation that adaptively changes the combination of modulation scheme and coding rate, the terminal to be controlled that belongs to the QoS class that requires band guarantee is accommodated in its own station when the adaptive modulation is performed. To the base station that executes control to determine whether or not it is possible,
For each combination, the allowable throughput of each terminal when a predetermined number of terminals are accommodated in its own station is calculated in advance, and for the terminal to be controlled, the minimum guaranteed rate of the terminal is compared with the allowable throughput, A determination procedure for determining a minimum physical rate for performing bandwidth guarantee based on the comparison result;
A control procedure for executing the control on the premise that adaptive modulation is executed at the determined minimum physical rate for the terminal to be controlled;   The program according to claim 13, wherein in the determination procedure, a combination having the lowest allowable throughput that satisfies the minimum guaranteed rate is specified from the combinations, and a physical rate of the specified combination is determined as the minimum physical rate. .   The program according to claim 13 or 14, wherein, in the control procedure, if a band corresponding to the determined minimum physical rate can be allocated to the terminal to be controlled, it is determined that the terminal can be accommodated.   The program according to any one of claims 13 to 15, wherein in the determination procedure, the number of terminals actually accommodated in the local station is monitored, and the predetermined accommodation number is determined based on the monitoring result. .

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